3Racing got bigger balls than Tamiya (ooooeerrr) I got big and little balls (no comments please)

Please help me before I start to lose my mind.:eh?:

Got a very frustrating problem with the Durga.

After two race meetings and 10 races started, I have failed to finish 6. One was due to me crashing and breaking a shock tower. One was caused by a connector shaking loose. But FOUR have been caused by the battery shaking itself apart at the battery bars.

I run 6-cells side-by-side, EP4200s with Much-More Premium bars.

I have tried glueing the cells together, taping the cells together, padding the battery tray out with foam, removing aforementioned padding. I have been using either a professional quality Weller 60W iron with a big tip or one of the 12V irons with a monster tip with Much-More 4% silver solder. And the packs are still breaking apart.

Next on my list of things to try is heatshrinking the whole pack together and using braid instead of bars to make the cell joints flexible.

Any other suggestions? I have never had this happen before expect for big crashes that have left the electronics hanging out of the side of the car, to have it happen so regularly now in normal race conditions is starting to spoil my fun.

Seems to me that the Durga chassis flexes a little more around the edges than you might think and the battery pack is taking the strain.

Anyone else having this problem? It would really help me to know I am not the only loony in the world who is suffering from this. :wtf:

I am running saddle packs - so I guess a lot less stresses involved. My pack does move around a bit in the car, do you find the same? I've not actually installed any foam though. I wonder is some sort of carbon fibre battery strap could solve your problem by stiffening things up a little bit?
I can't really see the chassis flexing enough to cause this - maybe it is, but I just can't see it. There ARE chassis' about that flex that much, but surely not the durga? :confused:

Did you scuff the ends of the cells a little with sandpaper or a dremel with a soft sanding whell before you soldered them? That usually helps with mine....

Try padding the bottom of the battery brace too. Might help by keeping the cells a little tighter with the padding underneath as well. I use foam sheets in 2mm from craft shops and stick them in with thin double sided tape. (you can colour-coordinate with hte foam as well ;))

don't scuff the cells.

If you are going to solder, use a small amount of flux on the cell before soldering. Thats how they should be done.

Chances are you have a mixture of a little cell vibration/movement and a slightly cold solder joint (not enough solder flow from the heat). Heatshrink will just compound the problem.

I get a little movement but not a lot, and it is tight around the motor mount. You could try turning the batt strap screws in a little more so the strap really clamps the cells, or put foam on the underside of the strap.

By scuff I really mean scuff not grind!

Proper solder has more than enough flux down the middle of it to get nice joints and the scuffing gives a better mechanical joint. Has always worked for me up to now and flux has always made a bit of a mess...

Im about to make an order on a couple parts at the moment. I am considering getting a back up "drive belt" . Can anyone suggest to me if this is nesacerry or not. Do the belts have a good life span or should i get one just in case for back up? Thanks.


A.J.

yeah get a spare belt. I've been through a couple of my 501X, one was from a stone getting in there (not a problem on the Durga) and the other was from running the front belt too tight.
You never know though - and it's worth being prepared.

Thanks for the advice Jimmy. Appreciated as always.

Diff Question
 

Is the 'Synthetic rubber cement' that is shown in the manual really the same stuff you get in a bike puncture repair kit? Also, I'm not sure about the 2 piece diff outdrive setup. I know it probably works OK in practice but it looks cheap and nasty - does anybody know if the 501X diff joints (TA-51286) or any other one piece part can be used instead? I am using Kanzen diff balls as I'd like to build the diffs as low-maintenance as possible.

Does any one have any idea what are those AW grease and the black grease that come with the durga kit for? seems like i didn't use any at all :confused: and how tight should the ball diff be for front and rear? thx

You should have used those greases. The thrust race should have either one in. The AW grease is for the driveshafts. I used AW grease to keep the pins in on the axles also.

Yes, the rubber cement is as used in puncture repair kits/trainer repair glue. Some debate over whether it is needed, I used a spot of superglue on them, some people just put a dab of ball diff silicone grease on the back of the plates, or you can leave them dry.

I always used to either leave them or put a dab of silicone grease on them, but the diff seemed to be slipping so I glued them this time.

Since then the diffs have been fine, they needed quite a bit of tightening after the first few runs bedded them in, but they didn't need attention at the last race meeting. I have a slipper clutch in now which no doubt helps take some of the strain off the diff.

I believe the 501X outdrives would be a direct replacement though, I might change to them if diff adjustment becomes an issue again.

Thanks Sosidge,

I'll get some new glue, that what I've got in an unopened puncture repair kit my nan bought me when I got my first 'big lads' bike might have matured a bit over the last 27 years!

Just priced up front and rear 501X outdrives and at $14.40 a pair plus postage from HK I am undecided whether to go this far yet, or just so how it goes. I will be running an LRP Vector X-11 7.5T brushless motor in it.

It'll either hang together or shred itself to pieces I suppose.

On the topic of the slipper clutch...

Tamiyas suggested setting is 3mm. I think this is too soft, and I was struggling for punch and braking. After bedding it in over a few packs 4mm seems to be better. This is using a 12-turn motor.

That's the way I always run things! If it breaks, upgrade, if it doesn't, leave well alone!:D

Brushed or brushless?

Brushed.

You are a wise man. I should have had you sitting on my shoulder over the last few weeks, I think with what I've spent on hop-ups on an unbuilt car (!) I could have imported a B44 for the same money. I just keep consoling myself that the main reason I bought the DB01 was so I can use my Trakpower lipo.

Another quick tip on fitting the slipper.

Put the 3 remaining 4x0.2mm shims from the original layshaft on the pulley side of the slipper layshaft to take out the slack.

Otherwise the layshaft moves around a lot, I noticed that the belt had been slapping against the slipper plate leaving black marks, may not be ideal for belt life.